Method and apparatus for melting glass



o. G. BURCH 2,975,224

METHOD AND APPARATUS FOR MELTING GLASS 5 Sheets-Sheet 1 March 14, 1961Original Filed 001.. l, 1954 4 IN VEN TOR.

OSCAR G. Buacu' FIELi. BY mafi) March 14, 1961 o. G. BURCH METHOD ANDAPPARATUS FOR MELTING GLASS Original Filed Oct. 1, 1954 5 Sheets-Sheet 224 T M i 1 m A VA VA lllllllllllllll| INVENTOR. OSCAR G. BuRcH A/4. M

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METHOD AND APPARATUS FOR MELTING GLASS Original Filed Oct. 1, 1954 5Sheets-Sheet 4 mm M 77 3/ o? 7 JNVENTOR.

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2,97 5,224 METHOD AND APPARATUS FOR MELTING GLASS Oscar G. Burch,Toledo, Ohio, assignor to Owens-Illinois Glass Company, a corporation ofOhio 13 Claims. (Cl. 136) The primary purpose of this invention is toprovide an increase in the productive capacity of a glass melting tanktogether with an increased quality of the glass produced. This increaseis to be accomplished by combining the action of two different heatsources, i.e., one being electrical and the other combustible fuel, usedparticularly in the melting of the glass, with the mechanical stirringaction provided by a gaseous agent, such as air or inert gas passing inbubble form upwardly through the melting glass batch.

In this invention it is contemplated to provide a furnace or tank havinginterconnected glass containing compartments separated from each otherby walls which are either submerged or otherwise, but each having aconnection with its adjacent portion by which molten glass may pass fromone to the other.

Also provided is means for feeding the raw batch materials into one endor one or both sides of the melting portion, either in stream, lump orblanket form, and further means is provided in said portion for stirringthe glass both by mechanical and convection current action.

In connection with the latter-mentioned feature, it is contemplated bythe present invention that stirring of the glass solely by mechanicalmeans disclosed herein will contribute greatly toward the meltingefficiency of the furnace, whether such furnace be heated solely bycombustible gases or by the combination of combustible gases andelectrical energy.

The heating means provided in this new arrangement is such that themelting batch and the resultant glass may be subjected to heat from bothcombustible gases and electrical energy both exteriorly and interiorlythereof respectively.

In the usual glass melting furnace, for example, one having a meltingand refining area, with said melting area being of several hundredsquare feet, provided with reversing side or end port checker firing, itis found that it will produce certain colors of molten glass on a basisof approximately one ton per six square feet of melter area.

The simple addition of a submerged dam before the throat or passageleading from the melter, will provide a condition whereby such a furnaceor tank, will produce molten glass on a basis of a ton of glass perseveral square feet of melter area.

The addition of certain electrical equipment to this same furnace willpermit production of molten glass on a considerably smaller number ofsquare feet of melter area and by adding bubblers, the square feet ofmelter area required per ton of glass produced is still further reduced.These increases of tons per square foot indicate an increase ofproductive capacity of approximately 35%, and actual production recordsindicate a considerable lowering percentagewise of off ware due to badglass even with the increased tonnage production.

Among the objects of this invention, it is desired to provide a novelmethod and means for facilitating the melting and refining operations ina glass melting tank United States Patent "ice 2 by producing adirection controlled and accelerated cir culation of the glass in thetank in such a manner as to control both the convection and the createdmechanical currents to promote a rapid melting and to reach the desiredhomogeneity in the melted glass in a shorter time period.

A more specific object of the invention is to provide means formechanically accelerating the motion of the glass in the melting orother areas by the introduction of a fluid or bubble forming material ormedium into the body of the molten glass insuch areas. Preferably thebubbling material is introduced through the floor of the melter, therebyto generate a vertical plane of accelerated motion in the glass bodycausing thereby a more rapid approach to the desired homogeneity in themolten glass.

The vertical plane of motion causes a circular or elliptical convectioncurrent which not only improves homogeneity but moves the glass or batchfrom the colder portion of the furnace to the hotter portion, where itis exposed to the heat source, thus promoting more rapid melting.Depending on its location, the induced vertical plane of motion may beused to oppose an undesirable convection current which would normally bepresent without the bubblers.

A further object of the invention resides in the utilization ofmechanical means acting within the mass of glass to facilitate movementof the glass and batch material from the colder portion of the furnaceto the hotter portion thus promoting more rapid melting, and, in thisconnection to control batch distribution in the molten glass body byinhibiting its tendency to sink to the lower strata of glass in thefurnace.

A still further object is to provide a further method and means wherebyhomogeneity in the glass body may be reached not only in greater volumebut in shorter time intervals. This is accomplished by providingenergized electrodes in various areas of the tank, but more specificallyin the melter regions where acting in combination with the radiant heatapplied to the surface areas of the glass, they produce convectioncurrent movement in the body of the glass. This in conjunction with andsupplemented by the mechanical action produced by the hubbling meansoperates to produce a more homogeneous body of refined molten glass ingreater volume and in shorter time intervals.

Another object is to utilize in combination, both combustion or radiantheating means and electrical heating means, respectively, externally andinternally of the body of glass being melted, together with a mechanicalmeans acting within the mass of glass to thereby provide a rapidincrease in the movement of the glass in and throughthe heating areas tothereby obtain a rapid increase in temperature to insure that all of theoxides will be brought into solution and with a resultant increase inthe tonnage of glass melted per square foot of melter area. Suchcombined heating also operates to control the movement of the glassforming the body of the mass.

A further object is to provide a greater movement of the entire body ofglass in the melter area, particularly through the depth thereof, andthereby cause a greater uniformity of temperature conditions throughoutthe depth, width, and length of the molten mass in the melting portion.

Other objects will be apparent from the following descriptive matter.

In the drawings:

Fig. l is a longitudinal sectional elevation through a glass meltingtank illustrating the combination of a submerged dam and bubblers.

Fig. 2 is a plan view of the glass containing portion of a melting tanksuch as shown in Fig. 1.

Fig. 3 is a plan view of a tank showing the addition of electricalequipment in equilateral triangular form.

Fig. 4 is a plan view of a further arrangement of the temperature andcurrent control members within a melting tank.

Fig. 5 is a cross-sectional elevation taken approximately at line V-V onFigs. 4, 6, 7 and 8.

Fig. 6 is a longitudinal sectional elevation through a glass melting andfining tank embodying the novelties of this present invention.

Fig. 7 is a plan view showing one arrangement of the members forcontrolling the current motion of the body of glass in a glass meltingtank.

Fig. 8 is a plan view of a further arrangement of the members adapted tocontrol the motion of the body of glass in a melting tank.

Fig. 9 is a plan view of an end portion of a melting tank showing asingle type batch feed as well as electrodes through the side walls ofthe tank.

Fig. 10 is a plan view of an end portion of a tank showing the opposedtype batch feeding.

Fig. 11 is a schematic wiring diagram of the electrical circuit for thetanks shown in Figs. 7 and 8.

Fig. 12 is a schematic wiring diagram of the electrical circuit for thecenter portion of the tank shown in Fig. 4.

Fig. 13 is a schematic wiring diagram of the electrical circuit for thetank shown in Fig. 3.

Fig. 14 is a part sectional elevational view showing the verticallocation of the horizontal electrodes of the tank shown in Fig. 9.

Fig. 15 is a cross-sectional elevational view taken on the longitudinalcenterline of a tank showing a bridgewall type structure as a dam.

Fig. 16 also is a cross-sectional elevation taken at the longitudinalcenterline of a tank showing a submerged opening through the dam.

Fig. 17 is a plan view of the structure of Fig. 16

showing the relative arrangement of the dam, the bubblers andelectrodes.

The present application is a continuation of my copending application,Serial No. 459,588, filed October 1, 1954; the latter-mentionedapplication being abandoned upon filing the present application.

Referring to Figs. 1-3, the tank, which may be generally of conventionalconstruction, comprises a floor 10, side walls 11, a roof 12, and endwalls 13 and 14, all madeof refractory material. A submerged dam orbridge wall 16 separates the melting compartment 17 from the refiningcompartment 13, said compartments being in communication through ingabove the submerged bridge wall 16. A series of pipes 25 supply coolingalong the bottom of the darn 16 to thereby prolong its life use. A mainbridge wall 20, with its complementary shadow wall 21, divides therefining and working compartments 18 and 22, respectively, but saidcompartments are in communication with each other through the passage 23at the lower end of the bridge wall 20 and around the ends and over thetop of shadow wall 21 as shown in Figs. 4 and 5. Passage 23 may be atany desired vertical level through the wall 20 or of the drop-throattype as shown.

Referring to Figs. 15, 16 and 17, modifications of the structure of thedam 16 are shown. In particular.the structure of Fig. 15 is importantfor several reasons. In this particular structure the submerged dam iscomprised of vertical walls 60 and 61 with a cap block 62 formingthereby a hollow structure having an opening 63 therein which extendsthrough the full width of the tank and which is open at the bottom andat both ends or sides of the tank.

Projecting up into opening 63 is a series of cooling pipes 65 which areadapted to blow cooling air upon the outer surface areas of the walls 60and 61 and the cap block 62. This cooling is provided only to prolongthe life of the blocks. 7

the passage 19 extendwithin the molten glass.

By providing this opening or gap 63 in this submerged dam, theelectrical currents from electrodes 27 and 35 are prohibited frompassage through the walls and are forced to travel through the moltenglass and over the dam through passage 66. In particular is this truewhen a circuit is provided which involves the electrodes positioned uponopposite sides of the dam. A row of bubblers 28 is provided in front ofthe dam and the electrodes 27 to modify the convection currents in thatarea.

A further modification of the structure of the dam is shown in Fig. 16wherein the submerged portion 70 extends through the bottom blocks ofthe floor of the tank and is cooled by pipes 65. Positioned immediatelyabove the submerged dam 70 is a floating dam 71, 71a and 71b which incooperation with the portion 70 provides a submerged opening 72 forpassage of the molten glass. If in this particular structure anelectrical circuit is pro vided as between the electrodes 27 and 35, thepath of electrical energy will be through the opening 72.

The several portions 71, 71a and 71b of the floating dam may beinterchanged to provide control of the size of the opening 72.

Fig. 17 illustrates the particular arrangement of the bubblers 28, theelectrodes 27 and 35 and the dam 71 with respect to each other.

The electrical circuits with respect to the electrodes 27 and 35 may beother than a circuit which passes the electrical energy over or throughthe dam as will be set forth hereinafter.

The raw batch materials may be introduced through openings in either theend or sidewalls, but the means for introducing said material is hereshown as batch feeders 15 in the end wall 13. These materials are meltedand refined to some extent as they advance slowly through thecompartment 17. The molten metal or glass then passes through thepassage 19 above the submerged bridge wall 16 into the refining chamber18 where it is further refined and conditioned before it is withdrawn ordischarged to the working chamber 22. Work openings 24 are provided inthe end wall 14 from which the molten refined glass may be taken in anyof the known conventional manners.

A blanket of radiant heat for melting the glass is supplied fromregenerators (not shown) for which hot gases are discharged throughports 26 which open into the melting compartment above'the level of theglass, said ports being arranged at intervals along both sides of thefurnace.

In addition to the blanket of radiant heat supplied through ports 26,there is provided a plurality of electrodes 27 which provide electricalheat in and through the mass of glass in the several glass containingcompartments. These electrical elements also aid in the control andproduction of the convection currents engendered in the body of theglass as will be more fully disclosed hereinafter.

As a component part of the invention, there is provided a series ofpipes 28 or lines which lead to and extend upwardly through the floor ofthe furnace and through which a fluid medium is discharged in the formof bubbles liberated at regulated and controlled intervals These pipesmay be of -cast iron or other metal, alloy or refractory materialresistant to the action of the molten glass and the high temperaturesinvolved.

The fluid or gas as it flows upward through the pipe 28 forms a bubble31 within the molten glass at the mouth of the tube, the size of thebubble being dependent primarily on the surface tension of the glass andin a measure on the shape of the tube or conduit at its discharge end.When the bubble reaches a certain size it will break loose from the endof the tube and commence to rise toward the surface of the glass. Thisupward movement of the bubble causes the comparatively viscous moltenglass which envelops it to move upward 5 therewith. This upward pull ormovement of the glass may be confined mainly to that portion of theglass immediately adjoining the bubble.

The gas or fluid supplied by each pipe is liberated within the glass ina succession of bubbles 31 formed at intervals which may be controlledand regulated by regulating the pressure. These bubbles, which may besubstantially spherical when released from the pipe 28, gradually expandas they rise and are also flattened out before they are discharged atthe surface of the glass.

In the normal feeding of glass batch to the usual melting furnace, itwill be found that the batch fills rather solidly down the end wall 13to the bottom wall and apparently the major portion thereof remainsthere or only small portions move slowly there-from. Because of thiscondition this end and bottom portion runs comparatively cold. Such acondition can be obviated by and through the proper use of the bubblers28 and regenerators (not shown) adapted to work in combination toprovide both mechanical and convection current circulation as set forthhereinafter.

The pipes 28 are preferably arranged in rows A and/ or B extendingtransversely of the furnace, these rows being at right angles to thegeneral direction of movement of the glass through the furnace. One rowof pipes A enters. through the furnace floor at a position in front ofand between and beneath each of the batch feeders 15. Row B entersthrough the furnace floor at a position before the submerged dam 16. Itwill be seen that with rows of pipes thus arranged and discharging gasbubbles at short intervals, there will be a continuous upward movementof these bubbles, all in a substantially vertical plane and distributedat short intervals throughout the area of the glass within such plane.Thus there is mechanically produced a rising path of molten glassextending through the width of the tank and which is drawn upwardly withthe gas bubbles. As a result the partially melted material which wouldordinarily be sluggish or dormant, so far as travel along or adjacent tothe bottom of the furnace may be concerned, is forced to move upwardtoward the top surface of the glass where the higher furnace temperatureand greater fluidity of the glass allow a comparatively rapid release ofthe entrapped gases. Thus these unmelted or partially unmelted portionsof batch material are subjected to the higher temperatures to materiallyaid in speeding the melting and fining process.

At the same time this movement of the glass in the form of a risingcurtain serves to prevent a rapid and continuous movement of the surfaceglass and batch materials directly from the charging end of the furnacetoward the fining chamber 18. The action is also such as to preventcomplete stagnation of the lower strata of glass in the furnace and toinsure the thorough mixing of the materials during the melting processwhile at the same time directing and supplementing the convectioncurrents and preventing the formation ofcords, streaks and otherconditions which would result in lack of homogeneity in the finalworkable glass mass. This controlled circulation of glass in accordancewith the present invention also accelerates the melting and refiningoperations and results in a substantial saving in fuel and an increasedproductive capacity.

The bubbles which are liberated within the glass may be comparativelylarge and will break upon reaching the surface of the glass. Theparticular type of fluid or gas used may vary, depending on whether itis desired to use an oxidizing, a reducing or a neutral gas for thepurpose of reacting on the glass. For example, where the glass batch.contains iron, an oxidizing gas may be used for oxidizing the iron. Areducing gas may be used to retain certain coloring compounds. A neutralgas may be employed where it is desired to avoid any changes in thestate of the chemical contents comprised in the glass, and such gas maybe supplied through pipes from a tank or reservoir in which the gas isstored under pressure although the invention is not to be considered aslimited to the use of gas in this form. Gas-forming elements orcompounds as, for example, air under pressure, water, ammonium nitrate,ammonium sulphate, sodium chloride, arsenic and other materials whichreadily form gaseous type bubbles, may be satisfactorily used where suchmaterials are delivered under properly controlled condition.

The rate of flow of fluid or gas may be varied throughout a rather widerange. In commercial operations I have obtained satisfactory resultswith rates of fiow ranging from as low as six bubbles per minutereleased from each line, up to 100 or more. The most satisfactory rateof flow depends upon variable factors met with in the melting and finingoperations such as size of he tank, depth of the glass, composition ofthe glass batch,.temperatures to which the glass is subjected duringmelting and fining as well as other factors.

Attention is directed to the row A of the bubbler pipes 28 and inparticular to their location with respect to the individual batchfeeders 15. It will be noted that these bubblers are so located that asthe bubbles form and rise to the surface of the glass they appear on thesurface in an area 32 of molten glass between each batch feeder. Onepurpose in having such an arrangement is to avoid any possible blowingof the dust of the batch mixture upwardly into the flame area of thetank, and thus cause rapid deterioration of the refractory members whichwould be exposed to such dust. These bubblers need not be locatedexactly midway between the batch feeders.

Referring in particular to Figs. 1 and 2, there is disclosed therein thecombination of bubblers 28, ports 26 and the submerged dam 16. With thisparticular combination, the batch materials are prevented fromaccumulating at the rear end wall 13 by the bubblers 28 and are forcedto come up into the high temperature surface zone portion where they aremore rapidly and individually subjected to such temperature. This willpermit a more rapid melting of these materials because a greateractivity in convection currents will exist through the length of themelter portion 17.

The submerged dam acts also in the capacity of forcing the glass to thesurface areas where it is again subjected to the high temperatureprovided by the ports 26.

Because of this mechanical and convection current activation, the glassmoving along the melter reaches a point of approximately complete fusionor melting in front of the dam 16, and because the top surface area isthe hottest, then only the hottest melted glass will flow throughpassage 19 into compartment 18.

Although this above described combination does increase the tonnagemelted, it is of course desirable to obtain the greatest tonnagepossible per square foot of melter area. As a consequence, a combinationsuch as just described but including additional heat supplied internallyof the glass provides the means whereby the ultimate in homogeneity ofthe glass and in tonnage melted may be acquired.

For example, the combination of bubblers 28, ports 26, dam 16, andelectrodes 27 will provide the desirable increase in melting, motion andfining of the glass. With the row A of bubblers 28 positioned betweenthe end wall 13 and the electrodes 27 and 27a, a vertical plane ofmotion is caused in the melting glass and the batch is thus preventedfrom settling down along the end wall 13 and to the bottom of thefurnace. This gives a much higher wall temperature on the bottom blocksand insures movement of the major portion of the batch and molten glassaway from this end of the furnace.

This row of bubblers A acting in conjunction with the electrodes 27, 27aand 27b (Fig. 3) provides a highly activated movement in the glass inthis end of the furnace, this action being the resultof the convectioncur- "7 rents generated in the glass mass by'the radiant heat of theports 26 and the electrodes 27, 27a and 27b supplemented by themechanical motion provided through the vertical plane of motion of thebubbles 31.

Because of this accentuated motion, all of the batch materials are morerapidly and in greater volume subjected to the radiant heat from theports 26 and that supplied by the electrodes 27, 27a and 271). Thisresults in the melting of a given quantity of glass in a much shortertime period than is usual in a normal furnace structure and operation.

With the batch being fed to this end of the furnace by a series offeeders there is thus effected what might be termed a blanket 33 of suchbatch mixture moving over the upper surface of the melting end of thefurnace 17 and extending part way through the length of the meltingportion of the furnace. In those instances where a single batch feeder15 or a pair of batch feeders, such as illustrated in Figs. 9 and 10respectively, may be utilized it will also be found that the majorportion of the batch tends to form small separate lumps or individualblankets 33. In such situations the current agitation produced by thebubblers 28 and the sidewall or floor electrodes 27, 27a and 27b willhasten the melting down' of the raw materials in such lumps or blankets33.

In Fig. 13 there is diagrammatically shown the electrical circuit forthe electrode arrangement disclosed in Fig. 3. As shown, it is a 3-phasecircuit with saturable reactors, etc., and adapted to automaticallyadjust the voltage, current and/or power in accordance with erosion and/or corrosion of the electrodes.

Referring particularly to Fig. 3, it will be noted that immediatelybefore the dam 16 are electrodes 27a and 27b arranged near the sidewalls of the tank, while electrode 27 is positioned near end wall 13,thus forming with electrodes 27a and 27b an approximately equilateraltriangle arrangement. These electrodes in combination with the radiantheat on the surface of the glass mass provide a path of hightemperature, between the blanket of batch 33 and the dam 16, to create aconvection current motion which restrains the flow of any of theunmelted batch material over the dam 16 and through passage 19.

The melted glass as it reaches the area of the electrodes 27a and 27b infront of the submerged dam 16, is subjected to such further temperatureincreases as may be required to bring the molten mass into a state ofrefinement that is almost complete. Also, it is contemplated that theseelectrodes will raise the temperature of the mass to a degree oftemperature which is compatible with the high rate of tonnage that willbe drawn from a furnace of this type. Thus, only the hottest glass willpass over the dam through passage 19 into the compartment 18.

As the molten mass enters into the compartment or chamber 18 (Figs. 2and 3), it may be then subjected only to radiant heat and will bepermitted to reach a condition of refinement which is free from bubbles.Subsequently the mass flows through the passage 23 into the workingchamber 22 from which it is taken for processing through work openings24.

With this above described arrangement of combined radiant and electricalheating, together with the bubblers at the batch feeding end, it ispossible to operate at a productive capacity of approximately a ton ofmolten glass per 4.5 sq. ft. of melter area.

Referring in particular to Figs. 6 and 8, it will be noted that a secondrow B of bubblers has been positioned in front of the dam and before theelectrodes 27:: and 27;. This particular row of bubblers B thus providesthrough the width of the tank, a second vertical plane of motionstarting from the bottom wall of the furnace and moving towards an uppersurface area of the body of glass. In addition, this vertical plane ofmovement apparently causes the glass to move in a path away from theelectrodes and toward the rear of the furnace, and

thereby increases the distance as between the dam l6 and the unmelted orblanket portions of batch 33 on the surface of the glass in the meltingportion 17 of the tank.

In addition, a further arrangement of the electrodes 27c, 27d, 27c and27 provide a path of convection cur rent motion which is accentuated bythe vertical plane of motion provided by row B of bubblers 28, therebycausing the glass in this particular area to move with great rapidityinto positions to be repeatedly contacted by the two heating means andthus have all its mass rapidly subjected to the heat both from theradiant heating as well as that supplied by the electrodes. Theglass atthis point may be at an extremely high temperature, and because of therow of bubblers B and electrodes 270 to 277, only the fully melted glasswill then pass over the dam 16 and through passage 19 into theconditioning chamber 18.

It should be apparent that with such an arrangement, that is, with thetwo rows A and B of bubblers 28 and two groups or sets of electrodes27c, 27d, 27e and 27, providing rapid motion in the mass of glass thatthe complete melting of the batch can be accomplished in a very shortperiod of time, and the needed high temperatures can be reached veryrapidly. Thus,

" with a very heavy pull of molten glass through the work openings 2-4,the required tonnage of glass batch may be melted on an extremely lowbasis of sq. ft. per ton, and it can be fined with sufiicient rapidityto meet any tonnage required to be drawn from the tank.

In Fig. 11, a typical diagram is shown as used with electrodes 270through 27 In this particular diagram a 3-phase, 3-wire power sourcesupplies a saturable reactor Stl and multi-ratio transformer in eachphase. The secondary windings of each transformer 51 are connected to apair of electrodes. The primary windings of each transformer 51 areconnected in series with the saturable reactor 50 to the power source.The saturable reactor 50 provides a means for conveniently adjusting thevoltage applied to the primary of the furnaee transformer andconsequently the voltage applied to the electrodes connected to thetransformer secondary windings. The saturable reactor 5t) may have itscontrol winding connected to devices which provide a control signalproportional to the voltage, current, power and/or combination thereof,applied to the electrodes or to the temperature of the glass in thevolume between electrodes or flowing. towards the electrodes, thusautomatically regulating the temperature of the glass and/or voltage,current, and/or power of the electrical energy applied in order toattain the most efiicient conditions for melting and fining the glassand to compensate for electrode erosion and/or corrosion.

The combination of multi-ratio transformer and saturable reactor orother type of voltage variator, permits complete regulation of thevoltage applied to the groups of electrodes 27 or 35 for melting ofglasses of widely different composition and electrical resistivity.

Electrodes for Figs. 3, 4, 6-9 and 14 may be of graphite, molybdenum orother refractory metals or conducting materials which are not rapidlyattacked or made soluble by the glass. As illustrated in Fig. 6, theelectrodes 27 may be adjustably mounted through the use of anywell-known adjusting means to permit regulation of the length of contactas between any electrode and the molten glass.

In Figs. 4 and 6, there is disclosed the same type of compartmentizedfurnace but in the conditioning chamber 18 a group or series ofelectrodes 35, 35a, 35b and 350 are positioned behind the dam 16 and inarow extending through the width of the furnace and before the openingof passageway 23 leading to the Working compartment 22. The addition ofthese electrodes in this chamber 18 permits the glass in this portion tobe subjected to highly active convection current motion as well as anydesired temperature condition conducive to the rapid elimination of anygas bubbles and to the increase in temperature that wili be needed inthe case of excessively high tonnage pull from the working chamber 22'.In Fig. 12 is shown a circuit basically identical to that of Fig. 11,with each multi-ratio transformer connected to a pair of adjacentelectrodes. In this particular arrangement there is thus provided meanswhereby external and internal heat are provided for both the melted andfined glass. The electrical circuit for electrodes 270 to 27, is thesame as that shown in Figs. 7, 8, and ll and may be controlledindependently of the circuit of Fig. 12, i.e., the electrodes 35 to 350.

In the particular arrangement of Fig. 4, there are provided three zonesof convection current activity between the point where the batch is fedinto the furnace and where it enters into the working chamber asworkable molten glass. At least two of these zones are supplemented by amechanical gaseous means, namely, the rows A and B of bubblers 28, whichaccentuate the speed of motion of the glass in a vertical plane andthrough this means the temperature of the body or mass of glass in thecompartments 17 and 18 becomes more nearly equalized and uniformthroughout its depth, width, and length.

Thus, with the combination of bubb-lers, gas ports and electrodes asillustrated in Figs. 4, 5, and 6, there is provided the ultimate incombining mechanical and convection current motion in the molten mass,and consequently all portions of the mass will more rapidly reach themaximum temperature and more rapidly bring the oxides into solution.Thus a greater tonnage withdrawal of melted and refined glass isobtainable in a minimum time interval. This arrangement permits theinput of B.t.u. into the mass to be upon a basis in proportion withtonnage pull upon the furnace or tank, and to also increase the tonnagemelted and worked per sq. ft. of melter area.

In applying electric power simultaneously to the heating zones on bothsides of the dam 16, 60 or 70, care must be exercised with certainrefractories and/or glass compositions to connect the transformers forthese two zones with the proper polarity and to the proper phases sothat the difference in voltage between electrodes on opposite sides ofthe dam, 27 to 350 and 27s to 35 for example, will not be of suchmagnitude to cause a high enough leakage current between these oppositeelectrodes and through the glass flowing over the dam or through therefractory material of the dam itself to superheat (boii) the glass ormelt the refractory darn, respectively. With other glass compositionsand/or suitable refractory material for construction of the dam, suchthat the leakage current will substantially flow only in the glass abovethe dam (rather than through the dam itself), this leakage current canbe used to advantage in the fining of the glass; since the depth of theglass over the dam is very shallow, thus a seed or glass bubble willhave a very short vertical distance to rise and burst. By attaining ahigh temperature in this shallow section of glass the viscosity of theglass is reduced permitting a much faster rate of rise of gas bubblesand'the decreased surface tension permits the bubble to break much morerapidly when it reaches the surface.

From the preceding descriptive matter, it will be found that the severalcombinations therein disclosed all tend to increase the quality andquantity of molten glass produced from a tank in any given time period.

For example, the first combination of radiant surface heat, a submergeddam and bubblers will measurably increase quality and quantity.

The second combination of radiant surface heat, electric heat interiorlyof the mass, a submerged dam and bubblers will further increase thetonnage melted per sq. ft. of melting area and improve the quality.

The third combination of radiant heat, a submerged dam, electric heat onboth sides of the dam, bubblers in front of the dam and interior-1y ofthe mass will still further enhance quantity and quality, and the fourthcombination which includes radiant heat, a submerged dam, electric heaton both sides of the dam and over the dam and bubblers before the damwill provide immeasurable increase in the quantity and quality of glassmelted and worked in a given time period.

The terms fluid and gas as used herein are interchangeable in theirscope and meaning as the use of either comprehends that the medium maybe actually of fluid or gas form.

Modifications may be resorted to within the spirit and scope of myinvention.

I claim:

1. The method of converting a mixture of basic glass making materials toa workable molten mass in a glass working tank having melting, finingand working areas which comprises the steps of initially feeding such amixture to the melting portion of said tank, applying heat to saidmixture during its progress through all said tank areas to formtherefrom a molten mass of workable glass, said heat being applied toboth exterior and interior portions of said mass during its progressthrough at least one of said tank areas, subjecting said mass toconvection current agitation during said heating, and modifying andaccelerating said agitation by introduction of a gaseous means beneaththe area of admission of said mixture.

2. The method in accordance with claim 1, wherein the exterior andinterior heating occurs concurrently with the accelerated agitation.

3. A furnace for the continuous production of molten glass through thecombined heat developed by electrical energy and combustible fuels,comprising a compartment type furnace having at least two interconnectedglass containing compartments, molten glass in each compartment, aportion of one compartment being so constructed as to melt rawmaterials, means to blanket feed raw materials along the end of saidportion, means to apply radiant heat over the entire surface area of theglass, a plurality of interconnected and energized electrodes in saidcompartment arranged in combination with said radiant heat to subjectthe glass in said compartment to convection current motion, at least oneof said electrodes being beneath the said blanket of raw materials andadjacent to a side wall of the compartment, means to regulate thesurface area of glass contact as between at least one electrode and theglass, means to automatically maintain a constant voltage to saidelectrode as the surface area of glass contact thereof changes, and atleast one gaseous introduction means modifying and supplementing theconvection current motion of the glass beneath the blanket of and at thearea of admission of said raw materials.

4. A furnace for the continuous production of molten glass through thecombined heat developed by electrical energy and combustible fuels,comprising a compartment type furnace having at least two interconnectedglass containing compartments, molten glass in each compartment, aportion of one compartment being constructed and arranged to melt rawmaterials, means to blanket feed raw materials over the surface of theglass and across the major portion of the end width of said portion, asecond portion of said compartment constructed and arranged to fine theglass, means to apply radiant heat over the entire surface area of theglass, a plurality of electrodes in said compartment arranged incombination with said radiant heat to subject the glass in saidcompartment to convection current agitation, at least one of saidelectrodes being beneath the said blanket of raw materials and adjacentto a sidewall of the compartment, means to adjust the lineal contact asbetween at least one electrode and the glass, means to automaticallymaintain the voltage constant with respect to said lineal contactadjustment, and a plurality of gaseous introduction means supplementingthe convection currents and operable to said compartment arranged incombination with said radiant heat to subject the glass in saidcompartment to convection current motion in a vertical plane through thewidth of the furnace and beneath said raw materials, at least two ofsaid electrodes being at a level beneath that of said raw materials andwith each adjacent to a side wall of the compartment, means to adjustthe lineal contact as between each individual electrode and the glass,means automatically maintaining the voltage constant in respect to saidlineal contact adjustment, and a plurality of gaseous introduction meansbeneath the said raw materials operable to cause motion of the glass ina vertical plane through the width of the melting compartment andbetween said first mentioned vertical plane of motion and an end wall ofsaid compartment.

6. A furnace for the continuous production of molten glass through theapplication to raw glass making materials of the combined heat developedby electrical energy and combustible fuels, comprising a compartmenttype furnace having at least two interconnected glass containingcompartments, molten glass in each compartment, means to apply radiantheat over the entire surface area of the glass, a portion of onecompartment being constructed and arranged to melt the raw materials,means to feed the raw materials along the end of said portion, aplurality of electrodes in said compartment arranged in combination withsaid radiant heat to subject the glass in said compartment to convectioncurrent agitation in vertical planes along the side and end wallsthereof, at least one of said electrodes being beneath the point ofadmission of said raw materials and adjacent to a side wall of thecompartment, means to vary the surface area contact as between at leastone electrode and the glass, a plurality of rows of gaseous introductionmeans modifying the convection current motion of the glass in saidcompartment and one of said rows being positioned along the end of saidmelting portion and beneath the area of admission of said raw materials.

7. A furnace for the continuous production of molten glass through thecombined heat developed by electrical energy and combustible fuels,comprising a compartment type furnace having at least two interconnectedglass containing compartments, molten glass in each compartment, meansto apply radiant heat over the entire surface area of the glass, aportion or" one compartment being constructed and arranged to melt rawmaterials, means to blanket feed raw materials over the surface of theglass and across the end width of said portion, a second portion of saidcompartment constructed and arranged to fine the glass, a plurality ofelectrodes in said compartment arranged in combination with said radiantheat to subject the glass in said compartment to convection currentagitation, said electrodes being beneath the said blanket of rawmaterials and adjacent to the side walls of the compartment, means toadjust the lineal contact as between said electrodes and the glass, aplurality of rows of gaseous introduction means arranged for modifyingthe convection currents and operable to supplement motion of the glassand one of said rows being beneath the blanket of raw materials andalong the outer end wall of the melting portion of the furnace.

8. A furnace for the continuous production of molten glass through thecombined heat developed by electrical energy and combustible gases,comprising a compartment type furnace having a plurality ofinterconnected glass fining of glass, means to blanket feed rawmaterials 7 through the end width of said compartment, a plurality ofelectrodes in said compartment arranged in combination with said radiantheat to subject the glass in said compartment to convection currentagitation in vertical planes, at least two of said electrodes beingbeneath said blanket of raw materials with each adjacent to a side wallof the compartment, said two electrodes arranged to generate aconvection current in a vertical plane beneath said blanket, means toadjust the lineal contact as between each individual electrode and theglass, and a mechanical gaseous introduction means operable to causemotion of the glass in a vertical plane extending through the width ofthe melting compartment along the end wall thereof and beneath the areaof admission of the blanket of raw materials.

9. A furnace for the continuous production of molten glass through thecombined heat developed by electrical energy and combustible fuels,comprising a compartment type furnace having at least two interconnectedglass containing compartments, molten glass in each compartment, thefirst portion of one compartment being constructed and arranged to meltraw materials, a plurality of means disposed along the end wall of saidcompartment and constructed and arranged to feed raw materials over thesurface of the glass and across the major end width of said firstportion, a plurality of electrodes in said compartment arranged incombination with said radiant heat to subject the glass in saidcompartment to convection current agitation, a pair of said electrodesbeing disposed beneath the point of admission of said raw materials andadjacent to a side wall of the compartment, means to automaticallymaintain the voltage constant with respect to any lineal contact changebetween said electrodes and the glass, means to provide a blanket ofradiant heat over the exposed upper surface area of the glass in eachsaidv compartment, and gaseous introduction means disposed between eachtwo points of admission of raw materials beneath the area of admissionofraw materials and operable to cause motion of the glass in a verticalplane parallel to and along said end wall.

10. A furnace for the continuous production of molten glass through thecombined heat developed by electrical energy and combustible fuels,comprising a compartment type furnace having at least two interconnectedglass containing compartments, means to provide a blanket of radiantheat over the exposed upper surface area of the glass in each saidcompartment, molten glass in each compartment, a portion of onecompartment being constructed and arranged to melt raw materials, meansto blanket feed raw materials along the end of said portion, a pluralityof electrodes in said compartment arranged in combination with saidradiant heat to subject the glass in said compartment to convectioncurrent agitation, at least one of said electrodes being beneath thesaid blanket of raw materials and adjacent to a side wall of thecompartment, means operable automatically to maintain a constant voltageto said electrode as the surface area of 'glass contact thereof changes,and a plurality of gaseous introduction means paralleling said blanketfeed means and constructed and arranged for modifying and supple mentingthe convection current motion of the glass beneath the area of admissionof the blanket of raw materials.

11. A furnace for the continuous production of molten glass through thecombined heat developed by electrical energy and combustible fuels,comprising a compartment type furnace having a plurality ofinterconnected glass containing compartments, molten glass in eachcompart ment, means to provide a blanket of radiant heat over theexposed upper surface area of the glass in each said compartment, one ofsaid compartments being constructed and arranged for the combinedmelting and fining of glass, means to blanket feed raw materials throughthe end width of said compartment, a plurality of electrodes in saidcompartment arranged in combination with said radiant heat to subjectthe glass in said compartment to convection current agitation, two ofsaid electrodes being beneath said blanket of raw materials with eachadjacent to a side wall of the compartment, means to maintain thevoltage constant in respect to any lineal contact change as between theglass and any electrode, and gaseous introduction means positionedbetween the said two electrodes and an end wall of the compartmentoperable to cause accelerated motion of the glass in a vertical planealong said end wall and through the width of the compartment and beneaththe feeding point of the blanket of raw materials.

12. A furnace for the continuous production of molten glass through theapplication to raw glass making materials of the combined heat developedby electrical energy and combustible fuels, comprising acompartment-type furnace having at least two interconnected glasscontaining compartments, molten glass in each compartment, means toprovide a blanket of radiant heat over the exposed upper surface area ofthe glass in all said compartments, a portion of one compartment beingconstructed and arranged to melt the raw materials, means arranged tofeed the raw materials adjacent the end of said portion, a submerged damin said compartment spaced from the said melting portion, a plurality ofenergized electrodes in said compartment arranged in combination withsaid radiant heat to subject the glass in said compartment to convectioncurrent agitation, said electrodes being beneath the level of said rawmaterials, before said dam and adjacent to the side Walls of thecompartment, said electrodes being so interconnected as to form a pathof electrical energy parallel to both said dam and side walls, automaticmeans to maintain the voltage constant with respect to variations in thesurface area contact as between the electrodes and the glass, andgaseous introduction means disposed along said end wall and constructedand arranged for modifying the convection current motion of the glassbeneath the point of admission of the raw materials.

13. A furnace for the continuous production of molten glass through thecombined heat developed by electrical energy and combustible fuels,comprising a compartment-type furnace having at least two interconnected glass containing compartments, molten glass in each compartment,a first portion of one compartment being constructed and arranged tomelt raw materials, a plurality of batch feeding means constructed andarranged to blanket feed raw materials over the surface of the glass andacross the end width of one end of said first portion, a second portionof said compartment constructed and arranged to fine the glass, asubmerged dam in said compartment spaced from said melting portion anddividing said first and second compartment portions, means to provide ablanket of gaseous radiant heat over the exposed upper surface area ofthe glass in each said compartment, groups of electrodes in saidcompartment portions arranged in combination with said radiant heat tosubject the glass in said compartment portions to convection currentagitation, one group of said electrodes being beneath the said blanketof raw materials and adjacent to the side walls of the compartment, asecond group of electrodes before said dam and adjacent the side wallsof the compartment, a further group of electrodes behind said dam andadjacent an end Wall of a com partment, means interconnecting at leasttwo of said groups of electrodes into a circuit of electrical energy,the electrodes adjacent the opposite sides of said dam beinginterconnected to pass electrical energy therebetween and angularly overthe darn, means to adjust the lineal contact as between at least oneelectrode and the glass, means to maintain the voltage constant withrespect to variations in the surface area contact as between theelectrodes and the glass, gaseous introduction means disposed onopposite sides of each batch feeding means and extending through thewidth of the compartment beneath the area of admission of the blanket ofraw materials and adjacent the end Wall of the melter, a further gaseousintroduction means adjacent the dam and beneath the surface of theglass, and both said gaseous introduction means constructed and arrangedto cooperate with at least a pair of electrodes to modify the convectioncurrents and to supplement the motion of the glass.

References Cited in the file of this patent UNITED STATES PATENTS1,741,977 Cornelius Dec. 31, 1929 2,263,549 Peyches Nov. 18, 19412,274,643 Adams Mar. 3, 1942 2,277,679 Borel Mar. 31, 1942 2,331,052Shadduck Oct. 5, 1943 2,387,222 Wright Oct. 16, 1945 2,636,913 LambertApr. 28, 1953 2,636,914 Arbeit Apr. 28, 1953 2,658,095 Arbeit et a1.Nov. 3, 1953 FOREIGN PATENTS 19,777 Great Britain of 1891 611,401. GreatBritain Oct. 28, 1948 629,811 Great Britain Sept. 28, 1949

